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Math Help - Solving inequalities involving ln

  1. #1
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    Solving inequalities involving ln

    , x (is a member of) [0,10]
    I started off by doing this
    2x+1>e^(3cos(x))
    dont know how to proceed.
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  2. #2
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    Re: Solving inequalities involving ln

    Quote Originally Posted by kandyfloss View Post
    , x (is a member of) [0,10]
    I started off by doing this
    2x+1>e^(3cos(x))
    dont know how to proceed.
    What exactly is the question? Solving the given inequality? What were the instructions? It cannot be solved by hand. You are obviously expected to use technology such as a graphics calculator to draw the graphs of y = ln(2x + 1) and y = 3cos(x) and then get an approximate solution.
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  3. #3
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    Re: Solving inequalities involving ln

    Yes, sorry i forgot to mention that. it asks you to solve the inequality.
    Here's my graph. I see ln(2x+1) > cos(x) when x>1 , right?
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  4. #4
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    Re: Solving inequalities involving ln

    Yes, but you should graph 3cos(x).
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    Re: Solving inequalities involving ln

    Quote Originally Posted by kandyfloss View Post
    Yes, sorry i forgot to mention that. it asks you to solve the inequality.
    Here's my graph. I see ln(2x+1) > cos(x) when x>1 , right?
    You need to zoom in a lot better than that since it's close to 1.5 where they cross. Note also what happens around x = 2\pi
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  6. #6
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    Re: Solving inequalities involving ln

    Quote Originally Posted by kandyfloss View Post
    , x (is a member of) [0,10]
    I started off by doing this
    2x+1>e^(3cos(x))
    dont know how to proceed.
    look at the graph of y = \ln(2x+1) - 3\cos{x} over the given interval and note where y > 0
    Attached Thumbnails Attached Thumbnails Solving inequalities involving ln-logcosgraf.jpg  
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